1. Field of the Invention
The invention relates to postcards and similar instruments for utilizing both sides of the document for recording information while simultaneously providing on a single copy sheet a duplicate bearing on both sides the same information as has been entered on both sides of the original.
2. Description of the Prior Art
There exists in the prior art a variety of duplicating forms which have been utilized in postcards, checkbooks, accounting sheets and other paper forms that employ a pressure sensitive paper or a carbon paper or some combination thereof in duplicating the information recorded on the original. The prior art duplicating devices include forms in which information placed on one side of an original sheet is duplicated either by means of a carbon or pressure sensitive paper on a retained office copy. The disadvantage of this type of duplicating device is that it is capable of recording information only on one side of the paper. In addition such duplicating forms are not suitable for use in the traditional sized single package postcard. Representatives of this class of postcards require either more parts, larger parts, or must furthermore be folded and joined prior to mailing and provide an odd sized copy for retention.
Another type of prior art duplicating device similar to the one described in U.S. Pat. No. 2,802,678 provides a duplicating form allowing the formation of a two-sided copy of a document by combining layers of carbon sheets, guard sheets and copy sheets as a means for recording information on one side of original and copy while preventing the simultaneous recording of information on the reverse side of the sheet. Duplicating forms of this type may be employed advantageously where the thickness of the original copies and guard sheets are maintained at a minimum. In addition, the guard sheets which prevent the duplication on both sides of the copy and original have the disadvantage of increasing the writing pressure necessary to record the informationn on one side of the instrument prior to the removal of the carbon and guard sheets and recording information on the other side of the document.
The problems involved with providing a single package duplicating form capable of clearly and accurately recording the same information on both sides of documents of the thickness and size of a standard postcard while providing a convenient sized file copy may in part be responsible for the proliferation of short letters and photocopies of documents having information recorded only on one side.
It has been a goal in the art of duplicating forms to provide a duplicating form with a reduced number of guard sheets necessary to prevent the recording of information on both sides of an instrument so that the heavier bond paper such as utilized in postcards may be used in duplicating forms. A further goal has been to provide a single package duplicating form that does not require bending or folding after the recording of information on both sides and which at the same time provides a clear two-sided copy of the original document.